TOPIC:

Double post, sorry, ignore, etc.

Post edited by: glenncarpenter, at: 2006/10/20 22:14

Thanks Kent, and I don't mean to be getting off on the wrong foot, but who exactly is helping here? Your initial suggestion that I check all the tuning basics was a good one, but other than that I have advice to visit the pharmacy for carb rubbers, a condescending admonition from WG that I'm on the wrong track, and three posts from you, which actually have good advice in them and which I appreciate. And a couple of welcomes, which I also appreciate.

Maybe I should start over.

When I get a new-to-me bike the first thing I do is to go through the mechanicals thoroughly and get everything working properly. Part of that is a tune-up, but often the first thing is to deal with some obvious problems so that I can get in some seat time and begin to form an impression of the bike. On the KZ I've changed the oil, lubed and adjusted cables and controls, cleaned the carb and bled the front brake. The most pressing issues right now are the carb issue, the grabbing clutch, the non-releasing front brake and the tires. I have a bunch of parts on order that will help me get some of that, and some other items, sorted out. But in the meantime, I'd really appreciate a few words of wisdom on these bikes that might be helpful in getting my fuel/air issues sorted out. So, humbly and respectfully, here is what I'd most like to know:

1) There may remain some very minor air leaks in the carb boots, so I will replace them. Where is the best place to buy these?

2) It is still running lean down low, but not too badly. I assume that this is some combination of lean factory jetting, the imperfect carb boots, and the K&N air filter. Offsetting that is the fact that at 5800ft I usually need a slightly leaner setup than at sea level (often stock EPA bikes actually carburate better up here, especially just off idle). I'd bet a whole set of valve shims that a one step pilot jet increase would be a benefit, but perhaps somebody here has been down this road before and found that not to be the case. Or found that two steps were necessary, or that a jet kit is the best way to go. I'd appreciate some input on all those things.

3) In the future, after I get everything else sorted out (or perhaps now, if there's an obvious benefit), I may be interested in some upgrades. CV carbs typically have advantages in efficiency over slide-throttle carbs. Are there any known carb swaps that benefit these bikes, such as CV carbs from a KZ750 or later KZ650? Maybe somebody has some experience or advice on that. I know some of the later KZs came with various different setups; a little wisdom as to what to avoid, what might work well, what HAS worked well, etc could really help me out.

So please, folks, if you have some pearls of wisdom to share, throw 'em at me. Really, I appreciate any and all advice, but look - I will absolutely guarantee that the issue I am dealing with here is a carburetor/air issue and not anything else. If I turn out to be wrong I will come back here and publicly tell you all about it.

Kent, these are good points, I'll let you know what I'm thinking and then maybe somebody can chime in if I'm off on something.

OKC_Kent wrote:

The K&N could be why you are running lean. I understand they flow so MUCH more air than stock.

Absolutely. I'm not about to go back to a stock filter, so part of the challenge here is that I don't have a truly blueprinted original setup to begin with.

You raised your needle to accomodate the extra air, and now you want to add a bigger pilot jet. You may really just need a bigger main jet and then that could mean lowering the needle and going back to the stock 15's pilots and turning those airscrews back to 1-1/2 out instead of 3.

As I understand it and have done it in the past, the best way to get jetting sorted is to start with the lowest circuit and work your way up to main. That way each change is not affected much by subsequent changes. My small air leak is probably affecting the idle jetting a little bit, but the midrange and top-end jetting very little. Main jet won't have any effect below 3/4 throttle or so; so I will leave that for last. Right now I'm betting that new carb boots and a 17.5 pilot will put me well in the ballpark for idle and low throttle settings. Maybe I'll be wrong, but changing the pilot jets back will take me maybe 20 minutes, so it seems like as good a next step as any. After that I may try lowering the needle one notch, back to stock (4th position from top I believe), but I think most likely the top position will prove to be the right one. As you said, the filter should flow enough more than stock to require a raised needle position. After that I will start messing with the mains, which are now 90s.

Sooner or later you'll get around to checking all the tuneup specs anyways. If those specs are off now, adjusting carbs at this point will just be wasted, as you would need to adjust carbs again when you tune it up, right?

More likely sooner. And I agree, in principle, that it's best to get the basics right first. On the other hand, it's best to set the ignition timing with the engine running, right? That way you can check the advance as well. And you can't really do that if it won't idle. And other than that and the air leak, which is now a very small one (if it still exists at all), there are no tuning parameters that will materially affect jetting unless they are WAY off - which I'm really darn sure they're not. If there were a misfire, or some other running problem that was consistent, I'd feel differently - but on the whole it really runs very well.

I'm probably beating this to death. My questions at this point don't really even have to do with carb tuning any longer, as that problem is well on its way to being solved. But like I said, if anybody knows something that might be helpful, I'm all ears. And still wondering about other carb setups, jet kits, etc.

We all like to help, and a little humor helps sometimes, and WG is a carb guy who knows the best way to get a carb problem sorted out is to just eliminate any other factors first.

Hey ,if you want a temp fix on the carb intakes, I have read of guys wrapping them in electrical tape, or coating them in silicone. Someone has vacuum bagged them in silicone too. Might be worth a shot until you get new ones.

My 78 650 B2 has 102.5 mains as stock. Your 90's are on the lean end, which may be ok at altitude, but could be way too lean with the K&N. I think you could run bigger mains and see an improvement. Last year a kz member had a 650 in Colorado, way high up the mountain. He had a pipe and pods. I think he wound up with 102.5 as his main jet.

If I get out of painting the bathroom Saturday, I might take a look at my own carbs, the plugs seem a bit rich/fouled. My needle is at #4 so I may raise the clip to #3 and give her a test. It's all fun, huh?

glenncarpenter wrote:

And still wondering about other carb setups, jet kits, etc.

Glenn, check this carb setup out

Hi Glenn,
As a day to day M/C tech, I can say that I have been tripped up before with seemingly carb related issues that improved after I tended to the ignition timing. It's still amazing to me sometimes how an engine with slightly retarded ign timing can seem to run a touch lean, but then after advancing the timing slightly the lean hesitation disapears. Point type ignitions will do this if not looked after, ask me how I know.
Take a quick glance at the point gap;)

Sorry for sounding condescending Glenn... gave the best and most sincere advice I could. I will drop out of this and I am sure others will be more capable of helping you. Good luck.